Capillary coupled heat exchangers



March 19, 1957 J. B. THOMAS 2,785,542

CAPILLARY COUPLED HEAT EXCHANGERS Filed Dec. 27, 1954 mur-2e @L ,27 le H95 |s Fig? Y INVENTOR. JESSE B.THOMAS BVMW ATTORNEY United States Patent() CAPILLARY coUPLnD HEAT EXCHANGERS `lesse B. Thomas, Louisville, Ky., assignor to Reynolds Metals Company, Louisville, Ky., a corporation of Delaware Application December 27, 1954,l Serial No. 477,836 6 Claims. (Cl. 62-117.55)

hln cooling apparatus, such as air conditioners, dehumidiflers, and the like, employing a heat exchanger contalnlng a volatile liquid, the evaporation of which produces a cooling effect, the gas or vapor is drawn off from the evaporator and compressed, the hot compressed gas is condensed in the condenser 'and then returned to the evaporator` to be evaporated. Various means may be employed to maintain a pressure differential between the condenser, and the evaporator, one such means being a capillary tube connection between the condenser and evaporator, and the present invention relates to such an arrangement.

It is an object of the present invention to improve the oper-ation of refrigeration `or cooling equipment employing a capillary tube.

A further object is the provision of an improved condenser and evaporator which may be constructed of a single length` of ftubing lt is a further object to obtain a `reduction in cost of manufacture of close coupled cooling or refrigeration apparatus by reducing the number of tube or pipe joints involved in` connecting the various parts of the system.`

According to the present invention acapillary tubehaving openings at `its ends extends -coextensively from one end of the condenser coil entirely within the contines of the coil, to one end of the evaporator coil entirely within the contines of the evaporator coil. The capillary tube carries liquid refrigerant from one end of the condenser coil counter-current to ilow of refrigerant inthe condenser coil, and discharges liquid refrigerant at the opposite end of the capillary tube into the end of the evaporator coil, so that ilow of liquid refrigerant through the part of the capillary tube located in the evaporator coil is countercurrent to ow of liquid and low pressure gas through the evaporator coil.

It is preferred to construct the condenser coil and evaporator coil of a single length of tubing bent to suitable shape, and when so constructed, the capillary tube is inserted in the length of tubing before the tubing is bent. The inlet for the condenser and the outlet for the evaporator are preferably located near the middle of the length of tubing with a suitable partition in the tubing therebetween, and the capillary tube passes through this partition in sealing relation thereto. In one form of the invention the capillary tube is inserted into the tube with a surrounding sleeve of sealing material attached thereto at the desired position, and the tubing then may be reduced to form a tight connection with the seal so that llow from the condenser to the evaporator can occur only through the opening of the capillary tube.

In a modication, the evaporator and condenser may be formed of separate tubes which are united by a separate middle section providing suction and hot gas connections with a sealing medium therebetween. In this modiiication the capillary tube is inserted into the middle sealing section first, and the capillary tube ends then are inserted into the condenserand evaporator tubes; these tubes lthen are attached to the sealing section; and the. tubes are then bent to shape.

The invention will be described in greater detail in the following specification taken in connection with the accompanying` drawing illustrating preferred embodiments by way of example, and wherein:

Figure l. is a cross sectional view diagrammatically illustrating one embodiment of the invention;

Figure 2 is an elevational view of the length of tubing;

Figure 3 shows a capillary tubehaving a sealing section attached;

Figure 4 is a view similar to Figure 2 with parts broken away to show the capillary tube and seal in place;

Figure 5 is ya cross sectional View of the bent tubing before insertion into the tins;

Figure 6 shows the middle portion of the tube, and

Figure 7 is a similar view of a modification.

Referring to the drawing there is shown a condenser, indicated generally at 1, and an evaporator indicated generally at 2. The condenser and evaporator are formed` from a single continuous length of tubing 3 bent at the condenser into a suitable sinuous shape and extending through radiation fins 5 and end plates 6;` and in the evaporator section the tubing is bent into sinuous form and passes through fins 8 and end plates 9.` The condenser and evaporator comprise a plurality of turns, but for simplicity eachis shown as having -only one turn, lil and 11 respectively. The middle portion 12 of the tube 3 provides an inlet branch 13 to the condenser, and an outlet branch 14 from the evaporator. As shown in Figure 6, the tube has holes 15 and 16 formed therein, and the short tubes 13 and 14 respectively are welded, soldered or brazed to the tube to form the inlet andl outlet connections. A sealing partition 17 is provided in tube portion 12 between the condenser inlet 13 and evaporator outlet 14. A capillary `tube 1S extends through this partition 17in sealing relation and the open ends 19, 20 of thecapillary tube extend into `the condenser and evaporator sections and terminate near the ends 21, 22 thereof respectively. The ends of the condenser and evaporator tubes may be closed in any suitable manner.

The lapparatus is constructed as follows: the plug 17 of neoprene or other suitable material is attached to capillary tube 18 in sealing relation, as by vulcanizing, as shown in Figure 3. Inlet and outlet connections 13, 14 are attached to the middle portion 12 of the length of tubing 3, by brazing, Welding or the like, as shown in Figure 2, and the capillary tube then is inserted through one open end of the tubing 3 until the partition 17 is positioned between the inlet 13 and outlet 14 as shown in Figure 4. The positioning of plug 17 `in tube 3 between the inlet and outlet may be gauged by a mark on the capillary tube, by measurement, by sighting through connections 13, 14, or in any other desired way. The ends of tube 3 then may be closed, or if desired, one end of tube 3 is closed before the capillary tube is inserted, and the other end is closed after the capillary tube is inserted. rThe middle tube portion 12 then is contracted about plug 17 by spinning or in any other suitable manner to provide a tight seal between partition 17 and the wall of tube 3. Thus, there is produced a long length of tubing 3 that houses the capillary tube, Which extends substantially from end to end, and as seen in Figures l and 4, there is a space 23 between each end of the capillary tube and the closed ends of the tube 3. The tube is then bent at its ends to sinuous form as shown in Figure 5, after which the iins are strung on. These latter operations may be carried out by collapsing the bends as described in patent 2,462,511 issued February 22, 1949 to N. Kramer, the collapsing of the ends being gauged so as not to constrict the capillary tube. The ends 13 andl Patented ,Man 19, 195,7v

l 14 then are connected respectively to the refrigerant cornpressor outlet and compressor inlet.

In operation, hot gas to be condensed enters at inlet 13 and ows through the condenser section in which it is condensed to a liquid. At the open end 19 the liquid refrigerant enters the capillary tube 18, as shown by the arrow, and flows through the capillary tube, counter current to the flow through the condenser tube to the evaporator section, where it is discharged at end 2li into the evaporator section as shown by an arrow. As the liquid flows through the evaporator section toward outlet 14 it absorbs heat and evaporates, the eluent vapors being discharged at the outlet 14.

It will be understood that the capillary tube will be selected to have the bore diameter required for its length to suitably restrict the flow of liquid refrigerant from the condenser to the evaporator so as to provide the desired pressure difference. The ends of the capillary tube may be out on a skew, if desired, to prevent engagement with the ends 21, 22 of tubes 3 blocking ow therethrough.

This construction is especially suitable for air conditioning or dehumidication systems where the condenser and evaporator can be close coupled. By employing one continuous length of tubing the piping is simplied and the number of joints to be made is reduced. Because the capillary tube is totally enclosed within the outer tubing 3, it is protected from mechanical injury, and it is in heat exchange relation with the fluid in the evaporator and condenser throughout its length.

In the modification shown in Figure 7, the middle portion 25 may be preformed with an integral partition 26 and integral inlet and outlet connections 27, 2S. The compression plug 17 is inserted in this modification against partition 26 and is held in place by the higher pressure in the condenser side. Or, if desired, the inside of the tube section 12 may be beaded, as indicated at 29 to form a compression lit with plug 17. After inserting the capillary tube, the unit 2S may be welded or brazed to the condenser and evaporator tubes.

I claim as my invention:

1. In a cooling apparatus: a condenser tube and evaporator tube forming a continuous length of tubing closed at its ends; a partition adjacent the middle of said tubes; a condenser inlet and an evaporator outlet for sai-d respective tubes adjacent the middle on opposite sides of said partition; and a capillary tube open at its ends eX- tending through said condenser and evaporator tube from closed end to closed end and in sealing relation through said partition, to provide counter current ow in the capillary tube from one end to the other relative to llow through the condenser and evaporator.

2. A cooling apparatus as specified in claim 1 wherein: the middle or" said continuous length of tubing comprises an inserted section having said partition therein, and having the condenser inlet and evaporator outlet connected thereto.

3. A `cooling apparatus as specied in claim 1 wherein: said partition comprises a deformable plug.

4. The method of forming a close coupled condenser and evaporator which comprises: forming a partition adjacent the middle lof a length of tubing; inserting an open ended capillary tube in said length of tubing in sealing Irelation to said partition and substantially coextensive in length with said tubing; closing the ends of said length of tubing; bending said length of tubing adjacent its ends t0 form sinuous condenser and evaporator coils; and forming condenser inlet and outlet connections in said tubing near the middle at opposite sides of said partition.

5. A cooling apparatus as specied in claim l wherein: said partition comprises a resilient deformable material; and said tubing is deformed inwardly to hold said partition in sealing relation to said tubing.

6. A cooling apparatus as specified in claim 1 wherein: said partition comprises a rigid metal wall, and a deformable sealing material engages said wall and said capillary tube to produce said sealing relation.

References Cited in the le of this patent UNITED STATES PATENTS 445,854 Lawrence Feb. 3, 1891 2,404,112 Urban July 16, 1946 2,565,145 Muly Aug. 21, 1951 2,708,307 Newell et al. May 17, 1955 

